1. Field of the Invention
The present invention relates to novel aminothiofluoran compounds and novel aminothiofluoran-.gamma.-lactam compounds. The invention further relates to processes of producing these compounds and recording members and elements containing these compounds as dye-forming materials or chromogenic materials e.g., color forming materials.
2. Description of Prior Art
Recording methods in which a color is formed, for example, pressure-sensitive copying materials, heat-sensitive recording materials, etc., employing colorless electron donating chromogenic materials (sometimes designated color forming materials or color formers) are already widely known and used commercially, and various colorless chromogenic compounds are known. In particular, fluoran compounds as examples of these colorless chromogenic compounds have preferred properties in that when they are brought into contact with an electron accepting developer (sometimes designated color developing materials or color developers) such as active clay, a phenol resin, etc., an immediate coloration occurs resulting in colors having a very wide range of various color tones and the colors or dyes thus formed have superior light resistance, water resistance, and color density. As a result of these desirable characteristics fluoran compounds have been actively investigated in this art and recording technique systems using these fluoran compounds have been greatly developed at present.
Processes for producing fluoran compounds in which the oxygen atom at the 10-position of the fluoran nucleus is replaced by a sulfur atom, that is, thiofluoran compounds represented by the general formula (VI) ##STR4## are reported in R. Meyer and J. Szaneck Ber., 33, 2577(1900) and Wyler Dissertation (Zurich 1894) but these investigators only reported that symmetric 3,6-substituted aminothiofluoran compound could be obtained by reacting fluorescein and sodium sulfide under alkaline conditions to form thiofluorescein, halogenating the thiofluorescein, and then aminating the product but no reports on asymmetric aminothiofluoran compounds are known. In this connection, the aminothiofluoran compounds of this invention represented by general formula (I) as will be shown below cannot be produced by the process reported by R. Meyer et al.